fossil fuels

Fossil fuels are carbon or hydrocarbon fuels, derived from what was living material, and found underground or beneath
the sea. The most common forms are coal, oil and natural
gas. They take millions of years to form. Their energy is only released
upon burning, when the carbon and hydrogen within them combine with the
oxygen in air to form carbon dioxide (CO2 ), or carbon monoxide
(CO) and water (H2O). Other elements within the fuels (such as
sulfur or nitrogen) are also released into the air after combining with
oxygen, causing further pollution with sulfur
dioxide and nitrogen oxide gases. In the case of coal, ash particles are also a problem.